1. Field of the Invention
The present invention relates generally to automated storage library gripper mechanisms, and more particularly to gripper mechanisms and methods for detecting and handling storage cartridges, e.g., magnetic tape cartridges, in automated storage libraries.
2. Description of the Related Art
Magnetic tape cartridges have proven to be an efficient and effective medium for data storage in computer systems. Large computer systems may utilize numerous cartridges for data storage purposes as well as a plurality of tape drives for inputting and outputting data to and from storage cartridges in a timely manner. Typically, as the number of storage cartridges grows they are organized in automated storage libraries. Automated storage libraries including magnetic tape cartridges may improve access speed and reliability of data storage systems having large numbers of magnetic tape cartridges.
Automated cartridge libraries generally include a plurality of storage bins or slots for storing library tape cartridges, a robotic cartridge gripping mechanism (often referred to as a “picker”), and one or more tape drives. The robotic picker may be controlled to select a specific storage tape cartridge from the library and transfer the tape cartridge between a storage slot and a tape drive within seconds. The robotic picker typically includes a gripper or hand mechanism positioned on the robotic picker. The robotic picker may position the gripper near a desired tape cartridge and activate the gripper to engage or grip the tape cartridge to remove the cartridge from the storage bin. The robotic arm may move the gripper and tape cartridge to a location to load the tape cartridge into a tape drive, load port (for adding or removing tapes from the library), and the like.
Storage cartridges are typically stored in storage slots stacked within the automated library. The storage cartridges are generally stacked with high density within a storage library housing to increase or maximize the storage capacity for a given size library housing. The density at which the cartridges may be arranged relies, at least in part, on the size and configuration of the gripper mechanism and clearance required to pick a storage cartridge. Typically, a gripper mechanism engages a storage cartridge with opposing gripper fingers on the top and bottom major surfaces of the cartridge. In this instance, storage slots are separated by sufficient distance or clearance for the gripper mechanisms to navigate between neighboring storage cartridges and storage slots during a picking process. The clearance between storage slots results in lower cartridge packing density within the storage library.
Gripper mechanisms may also include protrusions that interact with slots or notches on the cartridge housing. The protrusions may pull (or push) a cartridge in one dimension to remove (or insert) a cartridge from a storage bin or media drive. For example, a storage cartridge is pulled from a storage bin by a protrusion on the gripper mechanism to rest on a platform associated with the robotic picker mechanism for transfer to a media drive or the like.
Generally it is desired that a controller of the gripper mechanism be able to determine at a given time the state of the gripper fingers, e.g., open, closed, properly closed on a cartridge, or partially closed on a cartridge. For example, when a system is initially powered on, the location of the gripper fingers is desirably known so that actuators are directed to position the gripper fingers appropriately. One method for determining the state of gripper fingers includes moving an actuator slowly until it reaches a command current level, e.g., a spike in the current level associated with being in an open or closed position. This method, however, may be incorrect if the gripper fingers or system become jammed mid stroke. Further, the potential for damaging the gripper mechanism increases. Devices, such as limit switches may also be included in the gripper mechanisms, but generally add cost and complexity to the gripper mechanism.
Therefore, what is desired is a gripper mechanism for picking cartridges that allows for increased packing density of storage cartridges within an automated storage library. Further, a system and method for providing information to a gripper positioning controller associated with the state of the gripper mechanism, e.g., open, closed, properly closed on a cartridge, or partially closed on a cartridge, are desired.